Systems used in performing femoral and tibial resection in knee surgery

ABSTRACT

Tools for resecting tibia and femur include anchoring devices, a three-way alignment guide attachable to the anchoring devices, two embodiments of a resection guide attachable to the alignment guide and equipped with couplings for trackers, a plane probe for examining the resected plane, and apparatus for EM alignment of the resection guide in the event of a computer failure. The methods of the invention include operating a computer aided navigation apparatus in the conventional manner including attaching one or more trackers to the bone to be resected; choosing a location for the anchoring device with or without guidance from the computer and installing the anchoring device; attaching the three-way alignment guide to the anchoring device; attaching a resection guide to the alignment guide; attaching one or two trackers to the resection guide; locating the resection guide with the aid of the alignment guide and the computer; fixing the resection guide to the bone with pins. After the bone is resected, the resection plane probe may be attached to a tracker and moved about the resected plane to obtain feedback from the computer navigation system. In the event of computer failure, the methods include attaching the EM alignment guide to the resection guide; attaching the EM rod to the EM alignment guide; and locating the resection guide by visual location of the EM rod rather than by feedback from the computer navigation system.

1. PRIOR PROVISIONAL APPLICATION

[0001] This application relates to and claims priority from a pendingprovisional application Serial Number ______entitled “Methods, Systemsand Tools Used In Performing Femoral and Tibial Resection In KneeSurgery”, filed Feb. 28, 2001.

BACKGROUND OF THE INVENTION

[0002] 2. Field of the Invention

[0003] The invention generally relates to systems that may be used inperforming joint surgery; with a particular embodiment of the inventionbeing described, without limitation, in the context of kneearthroplasty. More particularly, with respect to knee arthroplasty, theinvention relates to systems used to properly locate and guideinstruments that resect bone in order to achieve a proper cut; andfacilitate the proper location and installation of artificial femoraland tibial prosthetic components.

[0004] 3. Brief Description Of The Prior Art

[0005] Total knee arthroplasty involves the replacement of portions ofthe patellar, femur and tibia with artificial components. In particular,a proximal portion of the tibia and a distal portion of the femur arecut away (resected) and replaced with artificial components.

[0006] As used herein, when referring to bones or other body parts, theterm “proximal” means closest to the heart and the term “distal” meansmore distant from the heart. When referring to tools and instruments,the term “proximal” means closest to the practitioner and the term“distal” means distant from the practitioner.

[0007] There are several types of knee prostheses known in the art. Onetype is sometimes referred to as a “resurfacing type”. In theseprostheses, the articular surface of the distal femur and proximal tibiaare “resurfaced” with respective metal and plastic condylar-typearticular bearing components.

[0008] The femoral component is typically a metallic alloy construction(cobalt-chrome alloy or 6A14V titanium alloy) and provides medial andlateral condylar bearing surfaces of multi-radius design of similarshape and geometry as the natural distal femur or femoral-side of theknee joint.

[0009] One important aspect of these procedures is the correct resectionof the distal femur and proximal tibia. These resections must provideplanes which are correctly angled in order to properly accept theprosthetic components. In particular, the resection planes must becorrectly located relative to three parameters: proximal-distallocation, varus-valgus angle and flexion-extension angle.

[0010] U.S. Pat. No. 5,916,219 (hereby incorporated by reference)discloses an apparatus and method for tibial alignment which allows theindependent establishment of two separate geometric planes to be used asa reference for the cutting of the tibial plateau during total kneearthroplasty.

[0011] Two separate frame assemblies with telescoping rods are attachedto the tibia with a fixed relative angle between them, thereby allowingalignment with the mechanical axis of the bone. A cutting block ismounted on one of the assembly frames and is positioned against thetibia. Stabilizing pins are then placed in the cutting block, allowingthe proper tibial plateau resection plane to be created.

[0012] The apparatus and method taught in the '219 patent, while solvingmany prior art problems as indicated therein, has a few disadvantages.The alignment apparatus must be removed prior to performing resection.The device ratchets to discrete locations, preventing a smooth(hereinafter defined as an “infinitely adjustable”) alignment. Further,the device can only be used to resect the tibia and cannot be used forfemoral resection.

[0013] Recently, various computerized systems have been introduced toaid the practitioner during different surgical procedures. A typical,commercially available system is described in the attached Appendix.Such systems typically include multiple video cameras which are deployedabove and around the surgical site; and a plurality of dynamic referenceframe (DRF) devices, also known as trackers, which are attached to bodyparts and surgical instruments.

[0014] The trackers are generally LED devices which are visible to thecameras. Using software designed for a particular surgical procedure, acomputer receiving input from the cameras guides the placement ofsurgical instruments.

[0015] The prior art instruments used for determining the correct planesfor tibial and femoral resection in total knee arthroplasty are not wellsuited for use with computerized systems. The known tools utilize eitherintra-medullary alignment or extra-medullary alignment techniques andmovement in three degrees of freedom is difficult or impossible.Moreover, in order to be useful with computer aided navigation systems,trackers must be attached to the tools. Existing tools do not permit orreadily facilitate the attachment of trackers.

[0016] Although computer aided navigation systems are superior tounaided visual navigation by the practitioner, computers have knownfaults. As every computer user knows, any computer can crash or fail insuch a way that it may take hours to repair. This is unacceptable duringa surgical procedure. Therefore, it is necessary to provide a backupsystem of some kind so that the procedure may be completed without thefailed computer.

SUMMARY OF THE INVENTION

[0017] It is therefore an object of the invention to provide methods,systems and tools for performing femoral and tibial resection andindeed, methods, systems and tools similarly useful in performingsurgery on other joints (implicit in the objectives and description ofthe invention set forth herein, although reference to the femur andtibial resection is specifically made for the sake of illustration).

[0018] It is also an object of the invention to provide methods, systemsand tools for femoral and tibial resection which allow location of acutting guide relative to three parameters.

[0019] It is another object of the invention to provide methods, systemsand tools for femoral and tibial resection which are infinitelyadjustable.

[0020] It is still another object of the invention to provide methods,systems and tools for femoral and tibial resection which are adapted tobe used with computer aided navigation systems.

[0021] It is also an object of the invention to provide tools which canbe used for both femoral and tibial resection.

[0022] It is another object of the invention to provide methods, systemsand tools for femoral and tibial resection which can be used withoutcomputer aided navigation systems should such a system fail duringsurgery.

[0023] In accord with these objects which will be discussed in detailbelow, the tools of the present invention (again, described in thecontext of knee surgery for illustrative purposes only), includeanchoring devices for attachment to the femur and the tibia, a three-wayalignment guide attachable to the anchoring devices and adjustablerelative to three parameters, two embodiments of a resection guideattachable to the alignment guide and equipped with couplings fortrackers, a plane probe for examining the resected plane, and apparatusfor EM alignment of the resection guide in the event of a computerfailure.

[0024] According to one aspect of the invention, the tibial anchoringdevice is specially designed to fit the triangular anatomy of the tibia.According to further aspects of the invention, the two resection guidesboth include rotatable pin guides to allow selection of anchoring pinlocation; one resection guide may be slotted and according to anotherembodiment of the invention, one is not slotted.

[0025] Further, according to one embodiment of the invention, theapparatus for visual EM alignment includes an EM rod and an EM alignmentguide (sometimes referred to as an alignment handle). The EM rod isattachable to the EM alignment guide and the EM alignment guide isattachable to the cutting guide. The EM alignment guide contemplated bya further aspect of the invention has two ends, one of which as adaptedfor femoral alignment and the other of which is adapted for tibialalignment.

[0026] The methods of the invention include operating the computer aidednavigation apparatus in the conventional manner including attaching oneor more trackers to the bone to be resected; choosing a location for theanchoring device with or without guidance from the computer andinstalling the anchoring device; attaching the three-way alignment guideto the anchoring device; attaching a resection guide to the alignmentguide; attaching one or two trackers to the resection guide; locatingthe resection guide with the aid of the alignment guide and thecomputer; fixing the resection guide to the bone with pins through therotatable pin guides; and resecting the bone.

[0027] After the bone is resected, the resection plane probe may beattached to a tracker and moved about the resected plane to obtainfeedback from the computer navigation system.

[0028] In the event of computer failure, the methods include attachingthe EM alignment guide to the resection guide; attaching the EM rod tothe EM alignment guide; and locating the resection guide by visuallocation of the EM rod rather than by feedback from the computernavigation system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029]FIG. 1 is a broken perspective view of the distal femur with ananchoring device according to the invention;

[0030]FIG. 2 is a side elevational view of the anchoring deviceinstalled in the distal femur;

[0031]FIG. 3 is a perspective view of the anchoring device installed inthe distal femur with a three-way alignment guide according to theinvention not yet attached to the anchoring device;

[0032]FIG. 4 is a view similar to FIG. 3 showing the alignment guideattached to the anchoring device;

[0033]FIG. 5 is a perspective view showing a first embodiment of aresection guide according to the invention not yet attached to thethree-way alignment guide;

[0034]FIG. 6 is a perspective view showing a first embodiment of aresection guide according to the invention attached to the three-wayalignment guide;

[0035]FIG. 7 is a side elevational view showing a first embodiment of aresection guide according to the invention attached to the three-wayalignment guide;

[0036]FIG. 8 is a perspective view showing a second embodiment of aresection guide according to the invention attached to the three-wayalignment guide;

[0037]FIG. 9 is a perspective view of a resection plane probe accordingto the invention;

[0038]FIG. 10 is a perspective view of a tibial anchoring deviceaccording to the invention;

[0039]FIG. 11 is a perspective view of a fail safe EM alignment guideaccording to the invention;

[0040]FIG. 12 is a perspective view of an extra medullary alignment rodfor use with the EM alignment guide shown in FIG. 11; and

[0041]FIG. 13 is a side elevational view of the fail safe EM alignmentguide attached to the resection cutting guide with the EM rod attachedto the EM alignment guide.

BRIEF DESCRIPTION OF THE APPENDIX

[0042] The attached ten page Appendix describes the parts and assemblyof a computer navigation system suitable for use with the invention. Thedescribed parts are commercially available and may be assembled by thoseskilled in the art according to the assembly instructions, incorporatedherein by reference.

DETAILED DESCRIPTION

[0043] Turning now to the Figures, the apparatus of the invention willbe best understood by a description of the methods of the invention withreference to the Figures.

[0044] As shown in FIGS. 1 and 2 an anchoring device 10 is installed inthe bone 1 in a region proximal to the lateral anterior cortex andwithin the incision. The location for the anchoring device may be chosenby eye or with the aid of the tracking/navigation software. As shown inthe Figures, the anchoring device 10 is a pin which is screwed into thebone. Other anchoring devices such as plates could be used, however.

[0045] With the anchoring device 10 in place, the alignment guide 12 islowered on to it as shown in FIGS. 3-5.

[0046] As seen best in FIG. 5, the alignment guide 12 has three camlocks (or equivalent means for releasably locking) 12 a, 12 b, 12 c. Thecam lock 12 a allows the alignment guide to be adjusted according tovarus-valgus angle relative to the anchoring device 10. The cam lock 12b allows the alignment guide to be adjusted according toflexion-extension angle relative to the anchoring device 10. The camlock 12 c opens the end of the alignment device to receive the resectionguide 14 shown in FIGS. 5-7.

[0047] Referring now to FIGS. 5-7, the exemplary depicted resectionguide 14 has a cutting guide surface 14 a, an attachment rod 14 b, apair of connectors 14 c, 14 d for connecting trackers (not shown), apair of rotatable pin guides 14 e, 14 f, and a pair of fail safemounting bores 14 g, 14 h.

[0048] The resection guide 14 is attached to the alignment guide 12 byopening cam lock 12 c and inserting the attachment rod 14 b into thealignment guide. It will be appreciated by those skilled in the art thatthe cam lock 12 c allows proximal-distal positioning of the resectionguide 14. After the resection guide 14 is attached to the alignmentdevice 12, a tracker is attached to the guide 14.

[0049] With the tracker attached, the first cam lock 12 a is opened andthe resection guide is moved in the varus-valgus plane until thenavigation software indicates the proper alignment. The cam lock 12 a isthen locked.

[0050] Cam lock 12 b is unlocked and the resection guide is moved in theflexion-extension plane until the navigation software indicates theproper alignment. The cam lock 12 b is then locked. The order ofperforming the aforementioned steps of unlocking and relocking either orboth of cam locks 12 a and 12 b, may be decided by the surgeon.

[0051] Lastly, the cam lock 12 c is opened and the resection guide ispositioned in the proximal-distal plane until the navigation softwareindicates the proper alignment. The cam lock 12 c is then locked. Withthe resection guide properly located, it may be affixed to the bone withpins (not shown) via the rotatable pin guides 14 e, 14 f. The pin guidesare rotatable so that the practitioner may choose the best site forinserting a pin. The next step in the procedure is to resect the distalend of the femur using the resection guide 14.

[0052] Those skilled in the art will appreciate that if the anchor pin10 is not substantially perpendicular to the varus-valgus plane, thesteps may need to be repeated to tune out error introduced by themisaligned anchor pin. One possible solution is to install the pin witha drill having an attached tracker thereby allowing the navigationsoftware to guide the placement of the pin.

[0053]FIG. 8 illustrates an alternate embodiment of a resection guide114. The resection guide 114 is identical to the resection guide 14except that it has a slot 114 a for the cutting tool (not shown). Somepractitioners prefer slotted cutting guides and others prefernon-slotted guides.

[0054] After the distal femur is resected, the accuracy of the cut canbe checked using the resection plane probe 16 shown in FIG. 9. The probe16 has a smooth planar surface 16 a and a coupling 16 b for attaching atracker. With a tracker attached to the probe, it is moved about theresected surface and the navigation software determines the accuracy ofthe resection.

[0055] All of the procedures described above can now be repeated toresect the proximal end of the tibia. Due to the triangular shape of thetibia, a special anchoring device 18, shown in FIG. 10, is used.

[0056] The anchoring device 18 has an anchoring post 18 a for attachingthe alignment guide, an angled body 18 b, a side slot 18 c, and a slotclamp 18 d. The anchoring device 18 is attached to the tibia byinserting a pin through the slot 18 c into the medial side of the tibiain a region within the incision and distal to the tibial tubercle. Theclamp 18 d is closed to clamp the slot 18 c relative to the pin (notshown).

[0057] It will be appreciated by those skilled in the art that the slot18 c has a plurality of grooves to snugly grab the pin. With theanchoring device 18 in place, the procedure described above is repeatedto resect the proximal tibia.

[0058] Although the computerized navigation systems are a major advancein arthroplasty, computers often fail and at most inopportune times. Thepresent invention provides a fail safe back up system for use when acomputerized navigation system fails.

[0059] Referring now to FIGS. 11-13, the invention provides a manual EMalignment guide 20 and an EM alignment rod 22. The guide 20 includes amounting shaft 20 a, two bores 20 b, 20 c for receiving the EM rod, afemur guide 20 d and a tibia guide 20 e.

[0060] The mounting shaft 20 a is inserted into one of the fail safebores (14 g, 14 h in FIG. 5) of the resection guide 14 and the EM rod 22is inserted into one of the bores 20 b, 20 c in the guide 20. When usedwith the femur, the EM rod 22 is inserted through the bore 20 c and thefemur guide 20 d is placed against the distal end of the femur as shownin FIG. 13. Flexion-extension and varus-valgus positioning may then beaccomplished visually using the EM rod. For use with the tibia, the EMrod is placed on the other bore and the tibia guide is placed againstthe proximal tibia.

[0061] There have been described and illustrated herein methods andtools for resection of the distal femur and proximal tibia. Whileparticular embodiments of the invention have been described, it is notintended that the invention be limited thereto, as it is intended thatthe invention be as broad in scope as the art will allow and that thespecification be read likewise.

[0062] For example, as indicated hereinbefore, the first two positioningsteps may be reversed in sequence, provided that the navigation softwareis suitably modified. Moreover, the clamps on the alignment guide neednot be cam locks, but could be other types of clamps.

[0063] Although the apparatus has been described as three separatepieces (the anchor, the alignment guide, and the resection guide), itcould be two pieces or a single piece. If it were a single piece, itwill be appreciated that separate devices would preferably be providedfor tibia and femur.

[0064] In general, as previously indicated, the methods and tools of theinvention could be used with other joints other than the knee. It isbelieved that the methods and tools could be used in arthroplasty of thehip, shoulder, elbow, etc.

[0065] It will therefore be appreciated by those skilled in the art thatyet other modifications could be made to the provided invention withoutdeviating from its spirit and scope as so claimed.

What is claimed is:
 1. A system for guiding the resection of a boneduring arthroplasty, comprising: a) anchoring means for anchoring thesystem to the bone; b) a resection guide coupled to said anchoringmeans; c) alignment means for locating the resection guide relative tothe anchoring means, said alignment means providing three degrees offreedom; and d) a computer navigation system coupled to said resectionguide.
 2. A system according to claim 1 wherein said computer navigationsystem is optically coupled to said resection guide.
 3. A systemaccording to claim 1 wherein said three degrees of freedom areinfinitely variable.
 4. A system according to claim 1 wherein saidanchoring means is a pin.
 5. A system according to claim 1 wherein saidanchoring means has an angled body and a side slot adapted to receive apin.
 6. A system according to claim 1 wherein said three degrees offreedom include two rotations and one translation.
 7. A system accordingto claim 1 wherein said three degrees of freedom includeflexion-extension, varus-valgus, and proximal-distal.
 8. A systemaccording to claim 1 wherein said resection guide is a guiding slot. 9.A system according to claim 1 wherein said resection guide includesmeans for attaching a computer navigation tracker.
 10. A systemaccording to claim 1 wherein said resection guide includes a rotatablepin guide.
 11. A system according to claim 1 wherein said resectionguide includes means for attaching a manual alignment device.
 12. Asystem according to claim 1 further comprising a manual alignment deviceremovably coupled to the resection guide.
 13. A system according toclaim 12 wherein said manual alignment device includes an alignmenthandle and an EM rod coupled to said handle.
 14. A system according toclaim 13 wherein said alignment handle has two ends, one of which isadapted to rest against the distal femur and the other of which isadapted to rest against the proximal tibia.
 15. A system according toclaim 1 further comprising a plane probe, said plane probe including aplanar surface and coupling means for coupling it to a computernavigation tracker.
 16. A system for guiding the resection of a boneduring arthroplasty, comprising: a) anchoring means for anchoring thesystem to the bone; b) a resection guide coupled to said anchoringmeans; c) alignment means for locating the resection guide relative tothe anchoring means, said alignment means providing three degrees offreedom, wherein said anchoring means and said alignment means need notbe removed from the bone prior to resection; and d) a computernavigation system coupled to said resection guide.
 17. A systemaccording to claim 16 wherein said computer navigation system isoptically coupled to said resection guide.
 18. A system according toclaim 16 wherein said three degrees of freedom are infinitely variable.19. A system according to claim 16 wherein said three degrees of freedominclude two rotations and one translation.
 20. A system according toclaim 16 wherein said three degrees of freedom includeflexion-extension, varus-valgus, and proximal-distal.
 21. A systemaccording to claim 16 wherein said resection guide includes means forattaching a computer navigation tracker.
 22. A system according to claim16 wherein said resection guide includes a rotatable pin guide.
 23. Asystem according to claim 16 wherein said resection guide includes meansfor attaching a manual alignment device.
 24. A system according to claim16 further comprising a manual alignment device removably coupled to theresection guide.
 25. A system according to claim 24 wherein said manualalignment device includes an alignment handle and an EM rod coupled tosaid handle.
 26. A system according to claim 25 wherein said alignmenthandle has two ends, one of which is adapted to rest against the distalfemur and the other of which is adapted to rest against the proximaltibia.
 27. A system according to claim 16 further comprising a planeprobe, said plane probe including a planar surface and coupling meansfor coupling it to a computer navigation tracker.
 28. A system forguiding the resection of a bone during arthroplasty, comprising: a)anchoring means for anchoring the system to the bone; b) a resectionguide coupled to said anchoring means; c) alignment means for locatingthe resection guide relative to the anchoring means, said alignmentmeans providing three degrees of freedom; and d) a computer navigationsystem coupled to said resection guide, said system being suitable foruse in resecting femurs and tibias.
 29. A system according to claim 28wherein anchoring means further comprises femoral anchoring means andtibial anchoring means.
 30. A system according to claim 28 wherein saidfemoral anchoring means is a pin.
 31. A system according to claim 28wherein said tibial anchoring means has an angled body and a side slotadapted to receive a pin.
 32. A system according to claim 28 whereinsaid computer navigation system is optically coupled to said resectionguide.
 33. A system according to claim 28 wherein said three degrees offreedom are infinitely variable.
 34. A system according to claim 28wherein said three degrees of freedom include two rotations and onetranslation.
 35. A system according to claim 28 wherein said threedegrees of freedom include flexion-extension, varus-valgus, andproximal-distal.
 36. A system according to claim 28 wherein saidresection guide includes means for attaching a computer navigationtracker.
 37. A system according to claim 28 wherein said resection guideincludes a rotatable pin guide.
 38. A system according to claim 28wherein said resection guide includes means for attaching a manualalignment device.
 39. A system according to claim 28 further comprisinga manual alignment device removably coupled to the resection guide. 40.A system according to claim 39 wherein said manual alignment deviceincludes an alignment handle and an EM rod coupled to said handle.
 41. Asystem according to claim 40 wherein said alignment handle has two ends,one of which is adapted to rest against the distal femur and the otherof which is adapted to rest against the proximal tibia.
 42. A systemaccording to claim 28 further comprising a plane probe, said plane probeincluding a planar surface and coupling means for coupling it to acomputer navigation tracker.